Skytec starter amps

[Area 51%]

The Aerovee assembly manual shows an unfused 14ga wire to energize the starter. I didn't care for the notion of an unprotected circuit, so I put a 15amp fuse in the system (maximum amperage for 14ga wire?). When the start button was pushed, the fuse popped immediately.
Upped the wire size to 12ga and put in a 20amp fuse. Pow! Fuse gone in an instant. Had to go to a 30amp fuse to keep them from blowing.
Anybody else have a fused starter energizing circuit, and what size fuse did you find necessary? 30amps seems like a lot to me.

[Bryan Cotton]

I also didn't like the unprotected wire. I've run it off my 25a main breaker. I haven't tried it yet.

[jrs]

I'm just in planning phase but had put in a 15amp fuse. These forums prevent a lot of trial and error on the part of the guys coming behind you in the build cycle. Thanks

[sonex1374]

The 14g wire to the starter only activates the starter solenoid, and should not have anywhere near 30 amps flowing through it (should only be 2-3 amps max). You might have that wire connected to the wrong terminal (e.g. the fat terminal that provides starting current to the starter), or there may be a wiring problem internally. I suggest looking these connections over and see if anything becomes apparent.

Jeff

[gammaxy]

I've measured the steady state current of the starter contactor at 6 amps Edit: 8.6 amps. I believe there's also a very substantial inrush current before the contactor fully engages that might be triple or more this steady state current. Skytec recommends the start button to be rated at 20A--I suspect this is where the requirement comes from. For what it's worth, I believe the only fuse I have on that circuit is a 25A fuse at the battery that hasn't blown yet :-) Edit: Turns out I do have a 10A fuse on that circuit

This interesting article from Bob Nuckolls explains how there's actually two coils on the starter solenoid to provide extra current to accelerate the Bendix and a reduced current afterwards for holding force:
http://www.aeroelectric.com/articles/strtctr.pdf

[Rynoth]

Mine is wired with 12AWG on a 20A fuse and the fuse has never blown. That 20A fuse is also protecting my main bus so I have some additional draw through it on startup for my engine instruments.

I did however have my starter button go bad, I believe it was 30A rated from Autozone. I don't know why it went bad but I got a better quality 60A rated button through Grainger and it's been good. I don't know if trying a different starter button might make a difference.

[sonex1374]

I've measured the steady state current of the starter contactor at 6 amps. I believe there's also a very substantial inrush current before the contactor fully engages that might be triple or more this steady state current.

Interesting. I did not measure the current to the solenoid, but this is higher than I would have thought. I flew my AeroVee for several hundred hours with a 7a fuse on the starter and it never blew. Clearly there's more going on inside the Skytech starter solenoid than a typical solenoid.

Jeff

[Area 51%]

The 14g wire to the starter only activates the starter solenoid, and should not have anywhere near 30 amps flowing through it (should only be 2-3 amps max). You might have that wire connected to the wrong terminal (e.g. the fat terminal that provides starting current to the starter), or there may be a wiring problem internally. I suggest looking these connections over and see if anything becomes apparent.

Not to worry. I've had VW cars most of my life and their starter set-up is the same as the Skytec. The wire was on the correct terminal. I did, however, remove the heavy cable from the master contactor to the starter to keep it from turning the yet to be filled with oil engine over.
I went as far as to install a low-draw (GM air-conditioning) relay with it's own fuse to keep from overloading my 30amp main bus circuit breaker as I also have the secondary ignition coils plumbed into that. I understand they draw 6-7amps (cold) all by themselves.
If 6amps is the working load on the starter solenoid, any chance a slow-blow fuse might keep things under control?

As long as we're on the subject of electrons (and their mysterious ways) does anybody know why My G5 boots up un-commanded every time the master is switched on?

[Rynoth]

You had the starter circuit open while engaging the starter solenoid? Makes me wonder if the solenoid circuit might draw more amps for some reason if the starter doesn't actually have its own power.

[Area 51%]

You had the starter circuit open while engaging the starter solenoid? Makes me wonder if the solenoid circuit might draw more amps for some reason if the starter doesn't actually have its own power.

Never gave that a passing thought. Didn't think it would matter if there was power flowing through the starter motor contacts or not.
It seems the second set of windings in the solenoid someone mentioned would have to get it's power from the main cable somehow.
I'll do a bench test to check though.